The usual Time Division Duplex (TDD) systems include the Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system in 3G network and the Time Division-Long Term Evolution (TD-LTE) system in 4G network.
FIG. 1 illustrates a frame structure in the LTE TDD system, where a radio frame has a length of 10 ms and includes ten subframes in total, including a special subframe and normal subframes, each of which has a length of 1 ms. The special subframe includes three slots including a Downlink Pilot Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Slot (UpPTS). The normal subframes are further categorized into uplink subframes and downlink subframes in which uplink/downlink control signaling, traffic data, etc., are transmitted respectively.
Seven TDD uplink (UL)/downlink (DL) configurations as depicted in Table 1 are defined in the LTE TDD system. In the seven TDD UL/DL configurations, the subframe #0 and the subframe #5, and the DwPTS slot in the special subframe are always used for downlink transmission; the subframe #2, and the UpPTS slot in the special subframe are always used for uplink transmission; and the other subframes can be configured for uplink transmission or downlink transmission as needed.
TABLE 1LTE TDD UL/DL configurationsSubframe indexConfiguration no.01234567890DSUUUDSUUU1DSUUDDSUUD2DSUDDDSUDD3DSUUUDDDDD4DSUUDDDDDD5DSUDDDDDDD6DSUUUDSUUD
In Table 1, D represents a downlink subframe, S represents a special subframe, and U represents an uplink subframe.
Static and semi-static TDD uplink/downlink configurations are typically applied in TDD systems earlier than the LTE R11. In the static TDD uplink/downlink configuration, it is a common practice to plan the network by determining and maintaining an uplink/downlink proportion according to the type of a cell and a general traffic proportion. In the semi-static TDD uplink/downlink configuration, the TDD configuration is altered during the system message updating procedure, the update periodicity of which is typically several days or even a longer period. The semi-static TDD configuration is updated particularly as follows: a User Equipment (UE, also referred to as a terminal) firstly fetches a paging message, and if the paging message indicates that the system message has been updated, then the UE fetches an existing TDD Configuration Information Element (TDD-config) in the SIB1 in a next system message modification periodicity to obtain the updated TDD configuration.
The Enhancement to LTE TDD for DL-UL Interference Management and Traffic Adaptation (eIMTA) mechanism supporting the dynamic TDD UL/DL configuration has been introduced to the LTE R11. The dynamic TDD UL/DL configuration can be altered per cell or per UE.
Once the TDD UL/DL configuration of the UE needs to be altered due to the dynamic TDD UL/DL configuration, an eNB needs to notify the UE, and at present there are the following several possible notification schemes for the dynamic TDD UL/DL configuration:
The scheme 1: a broadcast notification.
The scheme 1 can be further performed into the following three implementations:
In the implementation 1.1, a TDD UL/DL configuration notification Information Element (IE) is introduced to a Master Information Block (MIB), and the UE is notified of the updated TDD UL/DL configuration in the MIB, where the UE is forced to read the MIB at least once every several ms which can be a TDD UL/DL configuration update periodicity.
In the implementation 1.2, the R8 system message update procedure is reused, and the UE is notified of the updated TDD UL/DL configuration in the SIB1 or the MIB or another SIB.
In the implementation 1.3, the R10 Earthquake and Tsunami Warning System (ETWS) notification procedure is reused, that is, firstly the UE is paged to be notified that the TDD UL/DL configuration is altered, and then the UE reads a TDD UL/DL configuration indicator added to the SIB1 to obtain the updated TDD UL/DL configuration.
The scheme 2: the Radio Resource Control (RRC) signaling, that is, the UE is notified of the altered TDD UL/DL configuration in Radio Resource Control (RRC) signaling.
The scheme 3: the Media Access Control (MAC) signaling, that is, the UE is notified of the altered TDD UL/DL configuration in the MAC Control Element (CE).
The scheme 4: the Physical Downlink Control Channel (PDCCH), that is, the UE is notified of the altered TDD UL/DL configuration in a Physical Downlink Control Channel (PDCCH).
The shortest TDD UL/DL reconfiguration interval supported in the respective schemes is as depicted in Table 2:
TABLE 2The shortest TDD UL/DL reconfiguration intervalSchemeSchemeSchemeSchemeSchemeSchemeScheme1.11.21.3234The shortest406403202001010reconfigurationinterval (ms)
The respective notification schemes are applicable to the reconfiguration of the TDD UL/DL configuration per cell, but only the respective other schemes than the scheme 1 can be applicable to the TDD UL/DL reconfiguration notification per UE.
Due to the dynamic TDD uplink/downlink configuration introduced to the LTE R11, the UE may receive two TDD UL/DL configurations at the same time or in sequence, and in this case, transmission directions of the respective subframes can not be determined for the UE in the solution in the prior art.